#TeddersRecommends

Tremendous bandgap enhancement (up to 20% greater than the bulk value) is found in thin films of the workhorse material for oxide electronics-SrTiO₃, fabricated by pulsed laser deposition below 800 °C. The origin is comprehensively investigated. More importantly, it is utilized to tailor the electronic and magnetic phases of the 2DEG in SrTiO₃-based interface systems.

Germanene, a 2D honeycomb lattice analogous to graphene, is fabricated on a Pt(111) surface. It exhibits a buckled configuration with a (3 × 3) superlattice coinciding with the substrate's (√19 × √19) superstructure. Covalent bonds exist throughout the germanene layer. The resulting high-quality germanene enables researchers to explore the fundamentals of germanene and its potential applications.

A kind of multiwalled carbon-nanotube (MWCNT)/polydimethylsiloxane (PDMS) film with excellent conductivity and mechanical properties is developed using a facile and large-scale water surface assisted synthesis method. The film can act as a conductive support for electrochemically active PANI nano fibers. A device based on these PANI/MWCNT/PDMS electrodes shows good and stable capacitive behavior, even under static and dynamic stretching conditions.

Reduced graphene oxide (rGO) and polyaniline (PANI) assemble onto the surface of cellulose fibers (CFs) and into the pores of CF paper, to form a hierarchical nanostructured PANI-rGO/CF composite paper. Based on these composite papers, flexible and foldable all-solid-state supercapacitors are achieved.

A high-throughput electrocatalytic nano-bioreactor on tungsten disulphide nanosheets is demonstrated for the first time. The fundamental goal of this research is to develop a higher surface area, resulting in a greater enzyme loading and thereby increasing bio-catalytic activity within a nano-confined volume. As a result, the nanobio-system is capable of highly specific recognition of target bioanalytes, therefore, showing significant potentials in a range of bioreactor applications.

Upon the addition of silver nanowires (AgNWs), the electrical conductance of graphene film is improved. According to the film's optical birefringence, as shown by studies using liquid crystals (LCs), the improvements do not result from the chemical doping properties of the AgNWs; instead, they arise because the AgNWs facilitate connections among the domains in the graphene film. This is further supported by the film's Dirac point voltage, Raman spectra, and electrical resistance.

Halide perovskites solar cells have the potential to exhibit higher energy conversion efficiencies with ultrathin films than conventional thin-film solar cells based on CdTe, CuInSe₂, and Cu₂ZnSnSe₄. The superior solar-cell performance of halide perovskites may originate from its high optical absorption, comparable electron and hole effective mass, and electrically clean defect properties, including point defects and grain boundaries.

The electronic structure of the hybrid interface between ZnO and the prototypical organic semiconductor PTCDI is investigated via a combination of ultraviolet and X-ray photoelectron spectroscopy (UPS/XPS) and density functional theory (DFT) calculations. The interfacial electronic interactions lead to a large interface dipole due to substantial charge transfer from ZnO to 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI), which can be properly described only when accounting for surface defects that confer ZnO its n-type properties.

Arrays of nano-engineered carbon nanotube networks embedded in nanoscale polymer structures enable highly efficient charge transport as demonstrated by D. R. Barbero and co-workers on page 3111. An increase in charge transport by several orders of magnitude is recorded at low nanotube loading compared to traditional random networks in either insulating (polystyrene) or semiconducting (polythiophene) polymers. These novel networks are expected to enhance the performance of next generation hybrid and carbon based photovoltaic devices.

A branched architecture with ZnS backbones and ZnO branches is prepared by combining a facile thermal evaporation process and a hydrothermal growth. The application of nanofilm networks made of branched ZnSZnO nanostructures as a flexible UV photodetector is demonstrated by J. Liu, X. Wang, W. Tian, and co-workers on page 3088. The fabricated devices show excellent operational characteristics: tunable spectral selectivity, widerange photoresponse, fast response speed, and excellent environmental stability.

Multiferroic behaviour at room temperature is demonstrated in ε-Fe₂O₃. The simple composition of this new ferromagnetic ferroelectric oxide and the discovery of a robust path for its thin film growth by using suitable seed layers may boost the exploitation of ε-Fe₂O₃ in novel devices.

The rational hybridization of sp2 nanocarbon and nanostructured porous carbon into hierarchical all-carbon nanoarchitectures which inherit all the advantages of the component materials is demonstrated by Q. Zhang, F. Wei, and co-workers on page 2772. The sp2 graphene/CNT interlinked networks result in superior electrical conductivity and a robust framework, while the meso-/microporous carbon and the interlamellar compartment before the opposite graphene accommodate sulfur and polysulfides for lithium-sulfur cells with large sulfur loading, high discharge capacity, and stable cycling performance.

Reduced graphene oxide (rGO) films are decorated with arrays of Au nanoparticles using diblock copolymer micelles by T. D. Chung, B.-H. Sohn, and co-workers. On page 2764, they show how decorated rGO films can be transferred to various substrates including carbon electrodes and flexible polymer films without deterioration of the arrays. Decorated rGO films show high electrochemical activity for the oxygen reduction reaction (ORR), and a size-dependent ORR mechanism is analyzed electrochemically based on a rotating disk electrode.

A meaningful organic quantum well based on crystalline heteroepitaxy films is constructed. The quantum confinement effect is demonstrated by its reflections on optics and electrics: the blueshift of the optical characteristic peaks and the negative differential resistance at room temperature. The realization of an organic quantum well indicates the highly delocalized transport mechanism in well-defined organic crystalline systems and promises novel organic “quantum” optoelectronic devices.

An improved hydrothermal process is developed to fabricate macroporous graphene monoliths (MGMs) using a soft template of organic droplets. The MGMs are constructed from closed-cell distorted spherical pores. This unique microstructure makes MGMs that have low weight densities, good electrical conductivities, and excellent elasticity with rapid recovery rates.

Structural phase transitions driven by oxygen vacancy ordering can drastically affect the properties of transition metal oxides. S. van Dijken, L. D. Yao, and co-workers demonstrate on page 2789 that the focused electron beam of a transmission electron microscope can be used to control structural phase transitions in epitaxial La_2/3Sr_1/3MnO₃. The image is an artistic impression of the experiments. It consists of two scanning transmission electron microscopy images, one before and one after electron-beam irradiation, which are blended to illustrate the writing of a new structural phase in the area that is exposed to the electron beam.

Semiconductor-sensitized solar cells (SSCs) are emerging as promising devices for achieving efficient and low-cost solar-energy conversion. The recent progress in the development of ZnO-nanostructure-based SSCs is reviewed here, and the key issues for their efficiency improvement, such as enhancing light harvesting and increasing carrier generation, separation, and collection, are highlighted from aspects of surface-engineering techniques. The impact of other factors such as electrolyte and counter electrodes on the photovoltaic performance is also addressed. The current challenges and perspectives for the further advance of ZnO-based SSCs are discussed.

The recent developments regarding ZnO-nanostructure-based semiconductor-sensitized solar cells (SSCs) are reviewed. With the emphasis on surface-engineering techniques, a retrospective look at the extensive efforts in improving the energy conversion efficiency is taken, in particular, the approaches in enhancing light harvesting and increasing carrier generation, separation, and collection. It may offer a useful guide for the further advance of ZnO-based SSCs.

Radiosensitizers can increase local treatment efficacy under a relatively low and safe radiation dose, thereby facilitating tumor eradication and minimizing side effects. Here, a new class of radiosensitizers is reported, which contain several gold (Au) atoms embedded inside a peptide shell (e.g., Au_10–12 (SG)_10–12) and can achieve ultrahigh tumor uptake (10.86 SUV at 24 h post injection) and targeting specificity, efficient renal clearance, and high radiotherapy enhancement.

Advanced electrodes composed of mesoporous NiCo₂O₄ nanowire arrays on carbon textiles are efficiently fabricated by X. G. Zhang and co-workers. The electrode architectures presented on page 2630 promise fast electron transport by direct connection to the growth substrate and facileion diffusion paths provided by both the abundant mesoporous structure in nanowires and the large open spaces between neighboring nanowires, which ensures that every nanowire participates in the ultrafast electrochemical reaction.

Graphene has been known for its superior electronic properties ever since its discovery in 2004. The high aspect ratio and ballistic transport properties exhibited by this one-dimensional material are especially useful for electron emission applications. However, they are typically grown horizontally and excess efforts, such as the use of transfer techniques, is required to orientate them before effective electron emission from the graphene edges can occur. These transfer techniques have been shown to lead to additional defects to the as-grown graphene structure, thereby degrading its properties. Here, we present an approach to directly fabricate graphene onto metal nano-sized spindt tips (or nanocones) using the solid-state transformation of carbon deposited from a pulsed laser system at low temperature. Besides providing a layer of chemical and mechanical protection for the metal nanocones, the graphene-on-metal nanocones gave enhanced emission properties compared to bare metal nanocones. This was due to the reduction of effective field emission tunneling barrier, which was a result of graphene-metal charge transfer interactions. Controlling the metal nanocones density was also an important factor in determining the field emission performance, as electron screening from neighboring cones should be minimized.

Enhanced electron emission is observed when graphene is coated directly on metal nanocone (spindt-like) tips. The pulsed laser deposition technique is utilized to grow graphene directly on different arrays of cobalt and nickel nanosized cones at a low temperature of 700 °C. By comparing the electron emission properties across different types of metal nanocones, it is proved that the change in tunneling barrier at the emitter surface, instead of the physical aspect ratio, is the dominant factor in reducing the turn-on voltages.

A mere 2 nm conformal titanium dioxide overlayer coated by atomic layer deposition is shown to act as a blocking layer for high-efficiency solid-state perovskite (CH₃NH₃PbI₃) absorber-based solar cells. Surpassing the existing multilayer passivation, this ultrathin sub-nanometer layer leads to a photovoltaic power conversion efficiency of 11.5%.

Novel 3D metallic structures composed of multipetal flowers consisting of nanoparticles are presented. The control of surface plasmon hotspots is demonstrated in terms of location and intensity as a function of petal number for uniform and reproducible surfaceenhanced Raman spectroscopy (SERS) with high field enhancement.

Control of localized metal–organic framework (MOF) thin film formation is a challenge. Zeolitic imidazolate frameworks (ZIFs) are an important sub-class of MOFs based on transition metals and imidazolate linkers. Continuous coatings of intergrown ZIF crystals require high rates of heterogeneous nucleation. In this work, substrates coated with zinc oxide layers are used, obtained by atomic layer deposition (ALD) or by magnetron sputtering, to provide the Zn²⁺ ions required for nucleation and localized growth of ZIF-8 films ([Zn(mim)₂]; Hmim = 2-methylimidazolate). The obtained ZIF-8 films reveal the expected microporosity, as deduced from methanol adsorption studies using an environmentally controlled quartz crystal microbalance (QCM) and comparison with bulk ZIF-8 reference data. The concept is transferable to other MOFs, and is applied to the formation of [Al(OH)(1,4-ndc)]_n (ndc = naphtalenedicarboxylate) thin films derived from Al₂O₃ nanolayers.

The self-template route for the manufacturing of ZIF-8 films on silicon (Si) and quartz crystal microbalance (QCM) substrates involves the pre-deposition of ZnO films prepared by sputtering or atomic layer deposition methods and the subsequent conversion of the immobilized ZnO phase into crystalline and homogeneously dense ZIF-8 films via microwave-assisted synthesis.

Mimicking a natural touch requires not only softness, flexibility, compliance, but also robustness and high sensitivity to mechanical stimuli in the 3D space over a wide force range; this is a complex synergy to consider for the fabrication of performing tactile sensors. L. Beccai and co-workers propose on page 2659 an original and lowcost approach, which can inspire novel designs for artificial skins.